1. Field of the Invention
The present invention relates to a sheet for guiding regeneration of mesenchymal tissue, which is used when treating a deficit part of the mesenchymal tissue such as a bone, a cartilage, a muscle, fat or the like by a regeneration guide method, and a production method thereof.
2. Description of the Conventional Art
Realizing a medical treatment for regenerating biotissue and an organ in which there is a functional disorder or tissue/organ failure, is required. The regenerative medical treatment is a new medical treatment technique for reproducing biotissue, which cannot be recovered by inherently provided healing capability. This regenerated biotissue has the same form and function as those of original tissue and made with three factors such as a cell, scaffold and a growth factor.
In medical and dental treatments, bone regeneration by using own-bone has been widely used. However, for example, as a medical treatment of periodontal tissue with respect to the periodontosis having a bone deficit in a wide range, a tissue regeneration guide method has been developed. In the tissue regeneration guide method, it is necessary for a cell to keep a preferable interaction with a circumference condition thereof (a cell factor or an extracellular matrix), in order to grow and differentiate in the biotissue in a process during the regeneration of the periodontal tissue and realize the function of the cell. Then, when an initial condition of the regeneration process is suitably set up to thereby actuate self-repairing ability of the tissue according to the regeneration, the deficit part is recovered and repaired to a normal tissue. However, as for supporting tissue (fibrous tissue or a bone) of a tooth destroyed by periodontosis, if waiting the healing without doing anything, another soft tissue such as an epithelium or the like is entered to the necessary supporting tissue before regeneration, and thus there is a problem in which the supporting tissue of the destroyed tooth is not regenerated well. Then, in order to keep a space for regenerating the supporting tissue until regeneration of the necessary supporting tissue, a film-shape material is used to prevent the invasion of the unnecessary tissue, to thereby regenerate the supporting tissue of the tooth (for example, refer to The NIPPON Dental Review “The front line of the regenerative medical treatment on the basis of the biomaterial and the biotissue engineering” written by Yasuhiko TABATA, published by HYORON Publishers Co., Ltd., February 2004, volume 64, No. 2, p. 167-181). As the film-like material used for keeping the space for regenerating the supporting tissue until regeneration of the necessary supporting tissue, a semitransparent film such as an ethylene tetrafluoride resin film, a filter made with polyethylene or the like has been conventionally used. However, since these materials are non-bioabsorbable materials, it is necessary to remove these materials after the operation. Then, in recent years, the medical treatment by the tissue regeneration guide method has been widely used (for example, refer to Japanese Patent No. 2709349, Japanese Patent Application Laid Open No. 2002-085547). This treatment has an advantage that the film can be decomposed and absorbed immediately to vanish after the operation without remaining in the living body as a foreign matter, by using a film comprising a bioabsorbable material made with a bioabsorbable polymer material or a collagen, and thus the operation for removal is not necessary.
However, the tissue according to the regeneration has the low self-repairing ability, and thus the regeneration of the tissue may be hardly done only by preventing the invasion of the unnecessary tissue from the outside. In this case, for example, the following method has been used, that is, the cell, the growth factor or the mixture of those is contained into a polyglycolic acid nonwoven fabric or a porous hydroxyl apatite, and prepared by culturing it during a fixed period, and so obtained product is embedded in an applied part.
For example, a following technique for producing a biotissue filing body is indicated (for example, refer to Japanese Patent Application Laid Open No. 2004-105046). That is, a culture medium is stored in a production device of a biotissue filling body having a filling material layer and a dissolving layer in a container capable of storing, a culture medium. The filling material layer comprises a porous ceramics, collagen, polylactic acid, polyglycolic acid, hyaluronic acid or a material made by mixing those and has biocompatibility and/or bioabsorbability. The dissolving layer comprises a gelatin or the like and covers the upper surface of the filling material layer. When the cell is taken into the culture medium, the cell is precipitated and adhered on the surface of the dissolving layer to be grown along this surface. As time passes, the dissolving layer is dissolved to the culture medium to be disappeared. Thereby, the cell adhered on the dissolving layer adheres on the upper surface of the filling material layer comprising a biotissue filling material, and is grown continuously, where the biotissue filling material is originally existed at a lower part of the dissolving layer. As a result of this, the cell is grown by utilizing the biotissue filling material, to thereby produce the biotissue filling body. However, as for the bioactive ceramics such as calcium phosphate or the like, there is a problem that the cell is hardly grown in a base material. Further, the block-shaped filling material has low shaping property, so that it is difficult to carry out a treatment such as trimming or the like corresponding to the shape of the deficit part.
Further, the following technique for regenerating the tissue is indicated (for example, refer to Japanese Patent Application Laid Open No. 2003-010308). That is, a base material for regenerating cell tissue is formed so as to have various shapes, such as a sheet-shape, film-Shape, fragment-shape, sponge-shape, block-shape, fiber-shape or tube-shape in order to fill it to the deficit part of the tissue. This base material for regenerating cell tissue comprises hyaluronic acid and includes hyaluronic acid gel, which is not substantially modified by the chemical crosslinking agent or the chemical modifying agent, and hardly soluble in a neutral aqueous solution. Thereafter, a cell such as a chondrocyte, a stem cell, a marrow cell, an osteoblast, an ES cell or the like, and a material for guiding cell differentiation if necessary, are contained in the base material. This base material containing the cell and the material is filled to the deficit part in the living body, to thereby regenerate the tissue. At this time, the periosteum may be protected for the purpose of preventing the leakage of the cell, which is grown or migrated, from the deficit part. However, since it requires several weeks for differentiating the stem cell to a bone or a cartilage, the base material is decomposed during culturing of the cell on the base material comprising hyaluronic acid. Thus, there is a problem that the strength of the base material cannot be kept until the cell is transplanted into the deficit part.
Further, for example, the following technique is described for regenerating an alveolar bone (for example, refer to Japanese Patent Application Laid Open No. 2004-024706). That is a material obtained by uniformly mixing granular βtricalcium phosphate and a granular biodegradable material is formed to have a sheet shape, where the biodegradable material is softer than the βtricalcium phosphate. The mixture is heated to near the melting temperature of the biodegradable material to fuse the particles thereby making a porous sheet with remaining spaces between the particles. Thereafter, a sheet (for viable tissue regeneration guide) is prepared by laminating two porous sheets. An antibiotic is impregnated onto one side of the sheet, and a growth factor is impregnated into the other side. When this sheet is arranged by turning the side impregnated with the growth factor to the side of where the alveolar bone should be regenerated, and the side impregnated with the antibiotic to the side of gingiva, the sheet can prevent invasion of another external viable tissue into the space where regeneration of the alveolar bone should be guided. The other external biotissue is, for example, a gingival tissue or the like. Further, when alveolar bone regeneration is guided, the growth factor oozes out into the space and works to promote the growth of the alveolar bone. Then, the antibiotic works against fungi, bacteria or the like in the space where the sheet is provided to guide regeneration. However, the cells just after being removed from a culture dish do not produce sufficient amount of a substrate adhering to the sheet. Thus, there is a problem that the cell is cells are easily removed from the sheet thereby dispersing into a body soon after when it is seeded with the cells and transplanted.
In addition to this, a bone regenerating sheet is also indicated (for example, refer to Japanese Patent Application Laid Open No. 2003-275294). The bone regenerating sheet is made by laminating a cultured cell sheet and a biodegradable sheet, where the cultured cell sheet is made by culturing a mesenchymal stem cell into a sheet shape, and the biodegradable sheet is made of biodegradable substances shaped into a sheet. This sheet is transplanted to the deficit part, blocks the invasion of the tissue cell around the defect part to the deficit part, and promoting an osteogenic action. Thereby, the bone regenerating sheet can increase the repairing speed of the bone defect part. The bone regenerating sheet is made by sticking the cultured cell sheet to the biodegradable sheet using, for example, a fibrin paste or the like. The cultured cell sheet is made by the steps of cultured the mesenchymal stem cell on a culture dish, lowering the temperature of the culture dish to the predetermined temperature being lower than the culture temperature, and exfoliating it from the culture dish. The biodegradable sheet comprises, for example, the collagen or the like. However, the mesenchymal stem cell has multiple differentiation potency and, for example, according to an animal experiment, the property of differentiation to a bone, a cartilage, a fat, a blood vessel, a cardiac muscle or the like is proved. Thus, when the mesenchymal stem cell is transplanted to the defect part as it is, the cell may not be differentiated to the objective tissue.
In addition to the mesenchymal stem cell, another technique for regenerating cartilage is indicated (for example, refer to Japanese Patent Application Laid Open No. 10 (1998)-234844). In this technique, the chondrocyte is seeded in a material comprising the biodegradable polymer formed to have the sponge shape, grown, and embedded in the living body, to thereby regenerate the cartilage tissue. However, when the chondrocyte is used for regeneration of the cartilage tissue, the cartilage of a patient is taken out, cultured and grown at first, but it is hard to grow the chondrocyte in a culture system. Further, the regeneration efficiency of the cartilage tissue of the deficit part is low, and thus the burden given to a patient is large.